Means and method for internally detecting the presence of an intrauterine contraceptive device



United States Patent [72] lnventor MEANS AND METHOD FOR INTERNALLYDETECTING THE PRESENCE OF AN INTRAUTERINE CONTRACEPTIVE DEVICE WilliamL. Abramowitz FOREIGN PATENTS 332 994,400 6/1965 Great Britain 128/2524,516 OTHER REFERENCES Feb. 2. 19 Geyser :.1!PP 1. 12 Sept. 15, 1970'PrTmZT EhnIiher-wnnam E. Karnm Attorney-Ostrolenk, Faber, Gerb andSoffen ABSTRACT: A method and apparatus for detecting the presence ofcontraceptive devices which are either provided with a magnetized memberor are formed of a magnetizable material which is transverselymagnetized before positioning 5 Claims, 5 Drawing Figs.

in the uterus.

2 The detection device is comprised of an electronic circuit Int.coupled to probe means includes a magnefic core for Field 0 Search128/13, 2, generating an even harmonic function signal in the presenceof the contraceptive device detection being performed by 324/43, 47positioning the patient near the probe or passing by the probe and inclose proximity thereto. Nulling means are provided for [56] ReferencesC'ted cancelling out the effect of any extraneous field such as, forUNlTEDST-ATES PATENTS example, the earths magnetic field so that theextraneous 2,516,520 7/1950 Lamport et al 324/ 130UX fields will notaffect the sensitivity of the detection device in 2,752,564 6/ l 956Ryerson 324/43 the presence of the contraceptive device.

Patented Sept. 15, 1910 3,528,402

OSCILLATOQ l I W E SUPPLY n ,Am FLIP/ER.

ME T512 SWITCH ING Cnecwrs 65 9 firm/ s! I /4! Patented Sept. 15, 1970Sheet 3 of3 mic- 3 INVENTOR. W/JZ/fl/W z. xauw/wm/z 1 BY a farm; Ell4159557? zree {IQ/=1! 6 MF m MEANS AND METHOD FOR INTERNALLY DETECTINGTHE PRESENCE OF AN INTRAUTERINE CONTRACEPTIVE DEVICE This inventionrelates to an improved intrauterine contraceptive device (hereinafterreferred to as an IUCD) which is placed for long periods of time in thefemale reproductive tract, and to a novel method and apparatus forpositively detecting the presence and general position of such device.

The population explosion is a world-wide problem which has prompted manto seek contraceptive devices which are safe, reliable, and easy to use.Potentially, intrauterine contraception offers significant advantagesfor selected populations and individuals. Such advantages includedisassociation of the contraceptive method from coitus, subjectiveunawareness of the presence of the device, and freedom from thenecessity of constantly replenishing contraceptive supplies.

It is well established that a plastic or metal coil, ring or twistedshaped object placed by a physician into the uterine cavity will beeffective as a contraceptive. If such a device is properly designed asto size and shape it causes no discomfort to the wearer, may be worn forlong periods of time, and is almost 100 percent effective in itspurpose.

The most serious difficulty with intrauterine contraceptive devices isthat approximately one woman out of expels the device, usually withintwo months of insertion. The woman is often unaware of expulsion and 50percent of the IUCD contraceptive failures are a consequence of thedevice being expelled without the users knowledge. To guard againstunsuspected loss of the devices, many of the present lUCDs carry aplastic tail which protrudes slightly from the cervical opening. A womancan then examine herself to make sure that the device is in place.

Many forms of lUCDs, however, possess round ring or coil shapes whichcannot conveniently have extensions formed thereon. Moreover, thoseIUCDs which are provided withtails or other projecting parts havefrequently been found to be painful and uncomfortable. Additionally, theperiodic examinations necessary to ascertain the location of suchdevices may be painful or inconvenient. Such examinations, whenperformed by a physician, may be too costly.

It is therefore desirable to provide an external detection procedure forthe determination of the presence or absence, and general location of anIUCD within a womans body. (If present, it is in its correct location,otherwise it is expelled). Such a procedure would eliminate pain,discomfort and frequent physical examinations. I

Accordingly, a principal object of the present invention is to providean efficient and economical procedure for externally determining thepresence/absence and general location of an IUCD device within thewomans body.

Yet a further object is to provide an apparatus useful in the practiceof such procedure.

Other objects of the invention will appear as the following descriptionof preferred and practical embodiments thereof proceeds.

For a better understanding of the invention reference may be had to theaccompanying drawings, in which:

FIG. la is the basic circuit of the detection device to be used outsidethe body to detect the position of the IUCD; FIGS. lb and 1c areschematic diagrams showing alternative embodiments which may besubstituted for the circuitry of FIG. la;

FIG. 2 is a perspective view ofthe apparatus used for detection; and

FIG. 2a is a detailed view of an alternative probe which is employedwith the circuit of FIGS. lb and 1c.

The contraceptive element detected by one form of the present inventioncomprises a plastic intrauterine device, containing a magnetic coreelement. Such element, which is sealed within the walls of the IUCD soas not to come in contact with any vaginal secretions, is of a size andshape such that it does not materially decrease the desired flexibilityof the plastic body. Alternatively, the contraceptive element may be aspecially magnetized stainless steel Hall-Stone ring.

The detection apparatus is comprised of alternately saturable magneticmeans which, in the absence of any outside ambient, magnetic field willnot produce any even harmonic signals. However, in the presence ofexterior magnetic influences a significant second harmonic signal isgenerated and is indicated as such by a suitable indicating meter orother device. The detection means includes adjustable circuit means forsubstantially compensating for, or desensitizing (neutralizing) thedevice to the presence of the earths magnetic field, as well as to othermagnetic influences or disturbances which are located at appreciabledistances from the detection device relative to the contraceptive deviceto be detected.

The detection means is operated by first making suitable adjustments tothe device to null out" the earths magnetic field and other ambientfield steady state influences. The patient to be examined is thenpositioned in close proximity to the detection device probe which ispositioned generally within the re- .gion in which the contraceptivedevice is located but in all cases the probe is located exterior to thebody of the patient. No direct physical contact need be made with theextreme tip of the probe and the body of the patient. In fact, it isimportant that the patient does not contact the probe, because it mightmove, which could disturb the"null setting. Accordingly, a shield isprovided in close proximity to the detecting head, which shield thepatient may approach and even touch, without disturbing the setting. Thepositioning of the patient relative to the probe will cause asignificant deflection of the indicating meter if the contraceptivedevice is present in its proper location, thereby allowing for anexamination which may be made completely exterior to the body of thepatient and is in no way either atedious or a painful examination.

In accordance with the present invention the presence or absence andgeneral position of such magnetic element containing IUCDs andmagnetized Hall-Stone rings may be accurately and reliably detected bymeans of the devices illustrated in FIGS. 1a through 2a. It should beunderstood that the detector mechanisms shown in the drawings are sodesignated as to indicate the presence of any of the IUCDs, withindications depending upon the strength of the magnetic field generatedby any of these devices.

The detection device 40, shown in FIG. 2, is comprised of a housing 41containing the electronic circuitry of the detection device, as well asvarious control knobs and instrument readings, to be more fullydescribed subsequently, which are employed for the purpose of adjustingthe sensitivity of the device and nulling-out the effects of the earth'smagnetic field, as well as for providing an indication of the presenceof the IUCD.

The detection device 40 is further comprised of a probe member 42extending from one end of the housing, which device is maintained in asubstantially horizontal position by means of a supporting leg 43 havinga suitable base 44. The detection device magnetic core assemblies 45and/or 450 (in cases where two assemblies are employed) are housed atthe extreme end of the probe member 42 and will be describedsubsequently in more detail. The-device 40 may be placed upon anysuitable support such as a desk, table, and the like, with the supportleg 43 having an adjusting assembly 46 for adjusting the height of theprobe detectors 45 or 45a. The purpose to be achieved by the adjustmentdevice is to'place the probe detectors 45 or 45a at substantially'thesame level as the IUCD ispositioned withinthe womanbeing examined. Sincethe heights of various patients can differ the adjustable feature willallow for the adequate level positioning of probe detectors 45 or 45a.Alternatively, the probes 45 or 45a may be adjustably affixed to a tableand connected by wire cable to the control box. I

Referring more particularly to FIG. la, there is shown therein the basiccircuit employed for the purpose of providing for detection of the IUCDdevice. Before describing the circuit details of the detector device, itmust be emphasized that the magnetic moment, or detectability is verylow indeed for small magnets located in the range from 5-10 inches fromthe detector probe, which is approximatelythe body thickness of theperson being examined. Small magnets of the size compatible withintrauterine devices will not deflect an ordinary compass needle fromthis distance. The earths magnetic field, for example, has 300-500 timesas great an effect upon a compass, even when the intrauterine magnet isbrought up quite close to the compass needle. It is for this reason thatordinary detection means are ineffective and none of the prior artmeasuring devices, even those which are very sophisticated and extremelysensitive, have been able to provide for magnetic detection of suchdevices in the 5-10 inches distance range.

Strongly magnetized wire of approximately I" in length, and which may beinserted into one of the IUCDs will begin to be detectible by a compassneedle when positioned from W: away from the compass needle. If it ismoved a distance of (i.e.,2030 times further away) the amplificationfactor for detection varies as the third power requiring anamplification factor of 30 or 27,000. Even for an electronic device,this represents a high amplification factor. The cube law, as opposed tothe square law, becomes the necessary amplification factor for detectingthis type of magnetic device since both magnetic poles of the magnetbeing detected affect the detector device, with one pole aiding and theother opposing detection. This is due to the fact that the magneticmember has a relatively short length when compared to the detectiondistance.

Referring now to the circuit diagram of FIG. la there is shown thereinan oscillator circuit 51 comprised of first and second transistors 52and 53, which are driven by suitable power supply means 54 forgenerating current in their collector windings 56 and 57, respectively.The emitter windings 58 and 59, respectively, are coupled at a commonterminal 60 at which point a feedback path 61 is connected to feed backa portion of the output energy through a resistor R1 to the baseelectrodes of transistors 52 and 53. The feedback path sustainsoscillation thereby generating alternating magnetic flux in core 71having a predetermined frequency, f. It should be noted that only asingle core 71 is employed which is common to both the oscillator anddetector windings -they are on the same core separate toroids 71-71 areshown for clarity only. Lead 62 and lead 61 are power connections.Resistors R2, R6, adjustable resistor R3, adjustable resistor arm 63 andleads 64 and 80 provide the coarse adjustment voltage for the nullingcircuit to counteract the ambient field seen by the magnetometerdetector circuit 70. Voltage dropping resistor R5 is made adjustable toprovide for fine adjustment of the nulling voltage.

The detection device 70 is comprised of a saturable magnetic core 71having two pairs of oppositely connected windings 72 and 75 and 73 and74 wound on the same core which is driven by the oscillator means 51 forthe purpose of alternately driving the saturable core 71 into its twosaturation states. These pairs of second harmonic detection windingswound about core 71 will detect and provide a voltage output signalhaving a frequency 2f (where f is the frequency of the signal generatedby oscillator 51), which second harmonic output is a function of theconstant or d.c. magnetic field in the immediate region of core 71 suchas, for example, the earths magnetic field. Assuming that the detectiondevice 70 were placed in a medium in which there is no flux fieldwhatsoever, then no second harmonic signal would be generated, i.e.,theoutput of the pick-off coils would be zero. (It should be signal andproviding a visually observable indication of the presence or absence ofa magnetically polarized element such as an IUCD, for example. Normally,closed switch means 81 acts to short out the input leads 64 and 80 fromdetection device 70 until it is desired to take a reading and operatesin a manner to be more fully described.

It is well known that any magnetic system, driven beyond its saturationpoint, will contain only odd harmonic components in the absence of asteady (d.c.) polarizing flux field. The saturated flux system, in thepresence of a d.c. or biasing magnetic field, however, will contain allharmonics, both even and odd. In the detection system of the instantinvention, the earths magnetic flux field, as well as the magnetic fieldfrom the IUCD, produce the d.c. or steady biasing flux fields. These arethe influences that produce the second harmonic voltage, the magnitudeof which is measured to determine the presence or absence of theintrauterine device.

As was previously described, it is a practical impossibility to detectthe presence of a magnetically polarized member placed a distance from5-10" away from a compass needle and thus very much more sensitivedetection means are required.

It has been determined after exhaustive experimentation with smallmagnets of the type described herein held 5--l0" away from the detectiondevices 51 and 70 of FIG. 1a will produce a rectified d.c. output of anamplitude of the order of 0.070.l0 millivolts. It is therefore necessaryto provide an amplifier having the characteristics of providingextremely high gain and preferably being capable of being produced atrelatively low cost.

The amplifier device 90 of the instant invention, which provides thenecessary gain characteristics and which is quite inexpensive tomanufacture, is comprised of first and second interconnected transistors91 and 92 with the collector of transistor 91 being coupled to the baseof transistor 92 and with the collector of transistor 92 being coupledto a suitable current indicating instrument 93 such as, for example, amoving coil 1 milliamrneter instrument, through resistor R Thetransistors are so connected and adjusted as to have their steady stated.c. output, in the presence of no input signal, to be 0.5 milliampswith the input 94 being either opencircuited or short-circuited. This isto allow for subsequent switching operations. The amplifier then isproperly biased so that it becomes sensitive to the voltage changes inthe input circuit since the steady state condition is preliminarilyadjusted in the absence of any input voltage signal. The amplifiercircuit 90 has the additional advantage of providing a directionalcharacteristic in that the indication by the meter 93 will increase ordecrease with changes in magnetic polarization of the steady magneticflux field, from the initially set 0.5 milliamp condition.

The dotted rectangle 100 represents the adjustable double ganged switch47, also shown as being positioned along the 5 front face of the housing41, shown in FIG. 2. The adjustable noted that the d.c. field flux path140 is shown in dotted comprised of parallel oppositely connected diodes78 and 79 for the purpose of rectifying the output signal to form a d.c.voltage proportional to the second harmonic signal. The second harmonicsignal is coupled through a conductor into the control section 100which, in turn, is coupled to the input of the amplifier section foramplifying the rectified 75 amplifier power supply knob 47 controls theoperation of 2 double-four ganged switches S--0 through S-4 with themechanical coupling being shown by the dotted lines 101-101. With thecontrol knob 47 in the 0 position, it can be seen that all switches havetheir wiper arms out of electrical engagement, thereby disengaging theelectrical paths from the supplies 54a, 54b,

95, and 96. It can clearly be seen that sw itc h position o" constitutesthe OFF position of the detector device.

Moving control knob 47 to the 1" position, couples wiper arm 102 ofswitch S--1 to conductor 103, establishing a current path between thelower power supply 54b and resistors R1 and R2. At this time switch S--2has its wiper arm 104 electrically connected to conductor 105,electrically connecting the upper power supply 54 to common terminal 620and resistor R6. Switch position 1 of control knob 47 thereby energizesoscillator 51.

Simultaneously therewith switch S-S, which is ganged to control knob 47,establishes an electrical path between the and one terminal of meter 93.

Ganged switch S6, through its wiper arm 107a establishes an electricalpath from amplifier power supply 96 through switch S6 to the adjustablearm 97 of adjustable resistor R9. Thus, the amplifier is energized inreadiness for a detection operation.

The detection operation is performed as follows:

A l-milliamp full scale meter, is set to provide a one-half scalereading (i.e.,0.5 milliamps) by adjustment of the resistor R-l when theinput connections 64 and 84 see an open-circuit condition. The input 'tothe amplifier 90 can be seen to be open-circuited due to the fact thatthe wiper arm 108 of switch -3 is electrically disconnected from inputconductor 109 with the control knob 47 in position l and that the switchS- 7 has its wiper arm 110 disconnected from conductor 111, with controlknob 47 in the 1 "position. Wiper arms 108 and 110 can be seen to beconnected to the base of transistor 91 and to a ground potential,respectively, as shown in the amplifier circuit 90.

The input connections are then short-circuited by movement of controlknob 47 to position 2 coupling the input conductors 109 and 111 to thebase of transistor 91 and ground potential, respectively. The input isshort-circuited due to the normally closed position of the push-buttonswitch 81. In the short-circuited condition, the adjustable arm 97 ofresistor R-9 is adjusted in order to maintain the same deflection (i.e.,0.5 milliamp reading). One or two such adjustments of both resistors R9and R10 (shown on 40 also) may be necessary before placing the amplifierin use. Once these adjustments have been made, the open-circuitadjustment will maintain itself for very long periods of time. It may,however, become necessary to readjust the short-circuit condition duringthe use of the instrument, as will be more fully described.

A feedback path 99 may be provided between the collector electrode oftransistor 92 and its emitter through resistor R12 in order to providefeedback compensation for temperature drift and changes in thecomponents of amplifier 90.

The amplifier circuit 90 has been shown to have an amplification factorin the range from 30,000-60,000, depending upon the particulartransistors employed and thereby is well suited for use in detectorcircuits of 1a, lb, or 10 Due to the fact that the earths magnetic fluxfield is most overpowering in its effect upon the detection circuitryand will dominate by many fold the magnetic field which it is desired tomeasure, the first objective is that of neutralizing or nullingout theinfluence of the earths magnetic field.

This objective is achieved by aligning the detector device 40, shown inFIG. 2, into a fixed position upon its supporting surface and thenapplying a variable (plus or minus) voltage of an exactly sufficientmagnitude such that the amplifier will indicate 0" input (i.e., willprovide a reading of one-half scale).

The variable d.c. voltage is taken from the basic detector powersupply'54 and coarse and fine adjustments provided through theadjustable arms 63 and 65 of adjustable resistors R3 and R5,respectively, (knobs shown on 40, also), to provide for absolutely exactneutralization of the earths magnetic field. As a practical matter, ithas been found that a voltage of .3 volts d.c. maximum (plus or minus)is normally required to null-out the earths magnetic field, when it hasits maximum influence.

Once an exactly balanced condition is achieved, the instrument 40 isthen ready to indicate the presence or absence of the relatively smallmagnetic field produced by the intrauterine device. When the IUCD isbrought near the detector, a relatively strong indication occurs,depending upon its magnetic strength, its distance from the detector,and its angular (spatial) orientation to the major axis of the detectorpairs of coils 72 through 75. It should be noted that the detector ishighly directional and that the largest indications are directly alongthe dividing line major axis of the pick-off coils wound about magneticcore 71. These d.c. flux axes are shown as dotted lines in FIGS. 1a, lb.

The instrument once balanced, will detect not only the intrauterinedevices, but any and all changes in the ambient magnetic flux fieldstrength in which the detecting head 45 of FIG. 2 is located. Theambient field strength within the immediate locality of the instrument40 is strongly affected by automobiles passing along roads which may bewithin 50'J 5 l00, elevators in buildings, power line surges and thelike. In large cities such field variations become a major factor whichcan render the detection devices useless due to the presence of suchmajor disturbing magnetic masses and flux fields.

In order to minimize such disturbances, a pair of loading capacitances112 and 113 are provided in the control circuitry 100, whichcapacitances are coupled across the amplifier input line for the purposeof smoothing or averaging the amplifier output signal so that variableelectromagnetic influences such as moving traffic, elevators and thelike, will have less steady-state effect upon the indicator means 93.Although the capacitance devices tend to slow down the response to thedesired signal, which is a steady-state condition, the indicator needlewill tend to settle upon the steadystate condition while variabledisturbances generally tend to cancel or smooth themselves out duringthe detection process.

In operation, the detection device is short-circuited through thenormally closed push-button 81. Once the one-half of full scale positionis set in the manner previously described, the operator depressespush-button 81 momentarily to check the null position of the device. Afew trials will determine the best position to null out the earthsmagnetic field, as well as all other extraneous magnetic fields in thevicinity. The depression of the push-button 81 also determines theabsence or presence of any disturbing influences. If the disturbinginfluences are excessive, maximum shunting capacity may be employed byplacing the control knob 47 in the 3 position, placing the ganged switchS--3, wiper arm 108, in electrical contact with a common terminal 114 ofcapacitors 112 and 1 13. At this time switch S,0 couples capacitor 113in parallel across capacitor 112. Switch S-4, which has its wiper arm115 connected to ground potential, couples the opposite terminal 116,which is connected in common to capacitors 112 and 113, to a groundpotential, thereby placing both capacitors in the circuit to provide formaximum shunting capacitance. If the disturbing influences are not toogreat, the control knob 47 may be placed in the 2 position, placing onlycapacitor 112 across the amplifier input. If the disturbing influencesare insignificant, control knob 47 may be placed in the 4" position sothat no shunting capacitance is applied across the input to amplifier90.

The advantage of providing the normally closed switch 81 is that thecapacitors 112 and 113 are automatically discharged prior to eachdetection operation. The normally closed pushbutton also continuallyallows adjustable resistance R9 to be monitored and adjusted asnecessary.

If none of the above corrective functions are completely satisfactory,the entire instrument 40, shown in FIG. 14, may be reoriented in orderto seek out a position where interference is minimal. This is possibledue to the fact that the detector heads 45 and 42 are orientationsensitive and that the earths magnetic flux field has orientation withrespect to disturbances so that there are generally at least two minimumdisturbance orientations to which it is possible to orient the device.

In order to detect the presence of the IUCD, the patient may eitherstand motionless immediately adjacent the end of probe 42 or may pass bythe probe. It is not at all necessary that the patient make any physicalcontact whatsoever with the probe. In fact, it is preferred not to moveor disturb same, hence the use of shield 45b which substantiallysurrounds the probe 45. With a shield, or firmly fixed detecting head,the patient moves around and close to the head. This causes an indicatordeflection regardless of how the IUCD may be positioned in the person.If the patient did not move, there might be a possibility that the northand south poles might react equally and cancel out, in some cases. Indetermining the flux field situation at or before the instant of thedetection operation, the patient may or may not be positioned close tothe probe. There is no capacitance effect caused by having the patientstand in close proximity to the basic detector or amplifier which is amarked advantage over other devices such as metal detectors employingbeat frequency oscillators and the like.

It should be noted that while the device 50 of FIG. la employs anoscillator device employing a ferrite core member, other oscillatorcircuits may be employed which are capable of generating an oscillatingsignal of a suitable frequency.

FIG. lb shows an alternative detection circuit 50 (second harmonicdetection coils only-oscillator not shown), which may be substituted forthe detection circuit 50 shown in FIG. 1a and which is extremelyadvantageous for use in detecting IUCD devices of the type commonlyreferred to as a Hall- Stone Ring which is a circular coiled endlessspring having a diameter of approximately and being formed of 0.022"wire of #3 l6 stair less steel As of the present state of the art,

such l-lall-StoneRings have been undetectable except by X- ray, sonar,and probing. Such rings, however, are quite compatible with human tissueand do not adhere to internal parts of the body or cause any undesirablereactions. Such Hall- Stone Rings are preferably magnetized across amajor diameter so as to have one North and one South pole. The magnetismof the device, if driven to a staturating condition, will be retainedindefinitely unless brought into contact with another much strongermagnet. Due to the fact that the resulting magnet is much weaker in fluxfield strength than that obtainable by other means previously described,ambient field variations will have relatively more effect, therefore, itis necessary to modify the detection device in the manner shown in FIG.1b by providing a second detection coil circuit 70' which is coupledacross the detection circuit 70 at terminals 130 and 131 so as to beconnected with opposing polarities. The second detection coil servesautomatically to null out"in large measure, the earths magnetic fieldand any fluctuations thereof. The two sets of second harmonic detectionwindings are connected in parallel but with opposing polarities with oneset 72 through 75 bucking the other set 72' through 75'. These detectionmembers 70 and 70 are affixed firmly to a base member (not shown) andare arranged with their axes in exact alignment in the manner shown inFIG. Zn on the probe 42. All of the like coils as between the detectionunits 70 and 70' have the same number of turns, are mounted uponmagnetic cores of similar magnetic material and therefore, havesubstantially the same sensitivity to do. flux changes. Thus, once thedevice is properly set the reaction to changes in field strength remainsabout the same regardless of the direction in which the assembly ispointed.

However, the total magnitude (not sensitivity) of each separatedetection device is not exactly the same due to variations in windingdistribution, etc., and it is necessary to balance out this differenceby an external voltage similar to that described with reference to thecircuit of FIG. 13a. Thus, after the detector assembly is pointed in thedesired direction, the entire detection system is adjusted to a nullposition, bringing the indication of the meter to half-scale using thesame procedure as was previously described. This system is capable ofdetecting the presence of the magnetized Hall-Stone type rings alreadydescribed, as well as any of the other previously mentioned magnetizeddevices.

The arrangement of FIG. 1b has many virtues. Firstly, the device isquite immune to magnetic variations and other magnetic fluctuationsinherently found in large cities with disturbances such as passingtraffic, elevators, and power line surges having very little effect uponthe device. This makes it much easier to detect weak magnetic fieldswithout these fields being completely overshadowed by the earthsmagnetic field variations. Secondly, the detection system staysreasonably fixed once properly adjusted and it is not necessary to usethe manual push-button 81, previously described. The detection operationmay be performed by having the patient pass by in close proximity to thedetection coils which are held motionless during the test as waspreviously the case.

FIG. 1c shows a complete circuit alternative embodiment for detectingthe presence of a magnetized lUCD.

This embodiment is comprised of two toroidal cores, connected bucking,in parallel, for the detecting portions as previously described. The twocores appear as four cores for purposes of simplicity and only two coresare actually employed.

However, the oscillator portions for both cores are driven by only twotransistors 52 and 53, the same as previously described and shown inFIG. In. All windings are connected in parallel. The same transistorscarry twice the previous load, hence resistor R1 is to reduced toone-half its former value.

Also shown is a different arrangement for the indicating meter 93'. Amore sensitive 250:* -25 microammeter is used, which has its zerosetting maintained by an adjustable voltage dropping resistor R14. Asbefore, adjustments are made to resistors R9 and R10, to maintain andbring the instrument to its mid-point or zero reading. It should benoted that the 0.5 m.av operating condition is preset by proper choiceof resistor R15 in this embodiment. Resistor R16 is also provided toallow for two sensitivities, High" and Low, to give the instrument moreflexibility.

The switch 47, when closed puts the system in operation. Resistor R17 isadditionally provided to effect a fine balance between the two outputsets of windings. This is a refinement. Once set, this rarely would needchanging for the same general area and orientation. The positive side ofpower supply 54a is connected through switch S2 to adjustable arm 207 ofresistor R9. The negative side of power supply 54b is coupled throughswitch contacts S3 to the supply bus 208 of the amplifier section. Thepositive side of power supply 54b is coupled through contact pair S-4and lead 210 to one terminal of resistor R1. The parallel output windingpairs 7475, 74'- 75', have their common terminals 76 and 76'respectively, coupled across the terminals of adjustable resistor R17which, in turn, couples the resultant output through the rectifyingdiodes 78 and 79 to the base electrode of transistor 91 through lead211.

The detection members 70 and 70', as shown in FIG. 2a, are spacedapproximately 4"5" apart. The outermost assembly 70 yields the primaryindication for close magnets being detected, but both reactsubstantially the same for distant objects such as automobiles, theearths magnetic field, and so forth. For near magnets both assembliesreact, but the near assembly 70 has a far stronger effect than the farassembly 70, as shown by the relationship:

where X is the distance from the near or major assembly with X beingmeasured in units of the assembly spacing (4"to 5" From the aboveformula, if the assemblies are spaced 5" apart a magnet brought within5" of the detecting assembly in line with 70, will result in a net of 88percent effect due to the second assembly 70' being present. A magnet50"away from the device will have but 25 percent of the net effect andthis falls off quite rapidly with increasing distances. It should benoted that the remaining circuits 51, 54, 90 and of FIG. 1b aresubstantially identical to those shown in FIG. la and they have beenshown therefore in block diagram form for purposes of simplicity. FIG.10 shows clearly a simplified complete circuit, including all elements.

It can therefore be seen from the foregoing that the instant inventionprovides novel intrauterine devices and a relatively simple and yetsensitive method and apparatus for readily detecting the location ofsuch IUCDs.

While there has been described herein magnetic core means for detectingthe presence of magnetic fields, other devices may be employed fordetection of magnetic fields without departing from the spirit of theinstant invention. For example, Hall effect or magneto resistive effectdevices may be employed. Such devices are typically comprised of indiumantimonide or indium arsenide, which materials change their resistancein the presence of a magnetic field. Such materials are also directionsensitive. Readings can be obtained by passing a current through aconductor formed of a material having Hall effect characteristics, andreading the potential gradient developed across the current-carryingconductor.

Although there have been described preferred embodiments of this novelinvention, many variations and modifications will now be apparent tothose skilled in the art. In particular, I wish to point out that HallEffect probes, as well as magnetoresistive probes may be substituted forthe second harmonic magnetic field responsive detectors hereindescribed. Therefore, this invention is to be limited, not by thespecific disclosure herein, but only by the appended claims.

lclaim:

1. Means for detecting a magnetized contraceptive device adapted to bepositioned within the uterus of a subject wherein the detection occursas and when the subject moves past and in close proximity to thedetecting means, comprismg:

oscillator means for generating signals of a predetermined frequency;

a magnetic core;

first and second groups of windings wound about and magnetically coupledto said magnetic core;

said first group of windings being coupled to said oscillator means forcausing the signals of said oscillator means to drive said magnetic coreinto its opposite saturation states at a rate determined by the outputsignals of said oscillator means;

means coupled to said second group of windings for causing said secondgroup of windings to generate output signals only when changes in themagnetic satur'ation state of said magnetic core occur at a frequencyrate which is an even harmonic frequency of the operating frequency ofsaid oscillator means;

rectifier means coupled to said second group of windings for rectifyingthe output signals of said second group of windings;

amplifier means for amplifying the output of said rectifier means;

indicating means for providing a visual indication of said amplifiermeans output; and

D.C. power supply means including means for adjusting the output of saidpower supply means coupled to the first group of windings for saiddetector means for substantially canceling the effect of the earthsmagnetic field upon said detector means to improve the capability of thedetector means in detecting small magnetized objects.

2. The device of claim 1 further comprising capacitance means coupledacross the input of said amplifier means for smoothing the efiect ofspurious and variable magnetic influences upon said device; saidcapacitance means being adjustable to control the amount of smoothingdesired.

3. Means for detecting a magnetized contraceptive device adapted to bepositioned within the uterus of a subject wherein-the detection occursas and when the subject moves past and in close proximity to thedetecting means, comprismg:

oscillator means for generating signals of a predetermined frequency;first and second magnetic cores; first and second groups of windingsbeing wound about and inductively coupled to said first magnetic core;third and fourth groups of windings being wound about and inductivelycoupled to said second magnetic core; said first and third groups ofwindings being electrically coupled to said oscillator means to causethe signals of said oscillator means to alternately drive said first andsecond cores into their opposite saturation states; means coupled tosaid second and fourth groups of windings for causing said second andfourth groups of windings to generate output signals only when changesin the saturation states of their associated cores occur at a rate whichis an even harmonic frequency of the operating frequency of saidoscillator means; plural rectifier means being coupled to each of saidsecond and fourth groups of windings for rectifying the output signalsthereof;

amplifier means for amplifying the outputs of said rectifier means;

indicating means for providing a visual indication of said amplifiermeans output; and

the first and third groups of windings which are magnetically coupled tosaid first and second magnetic cores being coupled with their polaritiesopposing one another for substantially canceling the effect of theearth's magnetic field upon the detecting means.

4. The device of claim 3 further comprising adjustable voltage meanscoupled to the first and third groups of windings of said first andsecond magnetic cores for nulling out variations between said first andsecond detector means.

5. A method for detecting the presence of a magnetized member providedwithin a contraceptive device placed within the body of a subject bymeans of a magnetic detection means comprised of the steps of:

positioning said detection means in close proximity to that portion ofthe body of the subject containing said contraceptive device; providingrelative movement between said detection means and said subject;adjusting said detection means to eliminate the effect of steady anddistantly variable magnetic influences upon said detection device;developing an indication of the influence of the magnetic field of thecontraceptive device upon the detection device to thereby provide anindication of the presence of the contraceptive device as and when thedetection means is in close proximity to the body of the humancontaining said contraceptive device.

